When Solar Power Bends into a Phone Case: What is Flexible Photovoltaic Module Technology?

When solar panels are mentioned, most people probably envision dark blue or black glass panels installed on rooftops or ground-mounted power stations—heavy, rigid, and requiring fixed supports. However, with the advancement of technology, a brand-new type of photovoltaic product is changing people’s perception of solar power generation: flexible photovoltaic modules. Resembling a bendable solar film, they are extremely lightweight and can even be rolled up for portability, making the utilization of solar energy far more flexible and versatile.

This article will take you on a comprehensive exploration of this innovative technology, delving into its technical principles, application scenarios, and future development trends, while demonstrating how this revolutionary technology injects new vitality into the global energy transition.

1. Flexible Photovoltaic Modules: Redefining Solar Panels

Flexible Solar Panels (Flexible Photovoltaic Modules) refer to new-type photovoltaic products that use flexible materials (such as plastics, metal foils, or composite materials) as substrates, replacing the glass and aluminum frames in traditional photovoltaic modules. This enables the entire solar panel to possess bendable and lightweight characteristics. Though this material replacement may seem simple, it has brought about a fundamental transformation in the way solar energy is utilized.

The development of flexible photovoltaic technology did not happen overnight; it has undergone years of technical accumulation and breakthroughs. As early as the 1970s, scientists began exploring technologies for manufacturing solar cells on flexible substrates. However, limited by material performance and manufacturing processes, early flexible photovoltaic modules had extremely low efficiency and limited practicality.

In the 1990s, the development of thin-film solar cell technology brought a glimmer of hope to flexible photovoltaics. The application of thin-film cells such as CIGS (Copper Indium Gallium Selenide) and CdTe (Cadmium Telluride) on flexible substrates increased the conversion efficiency of flexible photovoltaic modules to over 10%, initially endowing them with practical application value.

Entering the 21st century, with advancements in materials science and nanotechnology, flexible photovoltaic technology entered a period of rapid development. Particularly since 2009, the emergence of perovskite solar cells has injected new vitality into flexible photovoltaics. Their laboratory conversion efficiency has rapidly increased from the initial 3.8% to over 25%, approaching the level of traditional crystalline silicon cells.

At the same time, flexible crystalline silicon cell technology has also achieved significant breakthroughs. Through ultra-thin silicon wafer technology and flexible packaging processes, traditional crystalline silicon cells have also achieved a certain degree of flexibility, providing more options for the diversified technical routes of flexible photovoltaics.

1. Core Technology: The Material and Process Revolution Behind Flexible Photovoltaics

The realization of flexible modules relies on advancements in materials science and battery technology. Currently, there are several main technical routes, each representing different technological innovations and application directions.

(1) Thin-Film Solar Cells: The Main Force of Flexible Photovoltaics

Thin-film cells are one of the primary technologies for flexible photovoltaics. Their defining feature is an extremely thin active layer (only a few micrometers thick), which can be directly deposited on flexible substrates. This “thin-layer” characteristic inherently gives them a flexibility advantage, making them the mainstream technical choice for current flexible photovoltaic modules.

1. Copper Indium Gallium Selenide (CIGS)

CIGS thin-film cells boast relatively high conversion efficiency—current laboratory efficiency exceeds 23%, and commercial product efficiency can reach 18%-20%. Due to the ultra-thin active layer, which can be directly deposited on metal foils or flexible polymer substrates, CIGS flexible modules are extremely lightweight, making them suitable for weight-sensitive application scenarios such as drones and satellites. Additionally, CIGS cells experience slow efficiency degradation in high-temperature environments, making them ideal for use in tropical regions or high-temperature settings. They also maintain high power generation efficiency under cloudy conditions or scattered light, suiting complex lighting environments like urban buildings.

However, CIGS technology faces certain challenges, primarily resource constraints and cost issues related to rare metals such as indium and gallium, which have restricted its large-scale application to some extent.

2. Cadmium Telluride (CdTe)

CdTe thin-film cells offer advantages of low cost and simple manufacturing processes, making them one of the most widely used thin-film cells in commercial applications. Compared with CIGS, CdTe requires lower raw material costs and features simpler manufacturing processes, making it suitable for large-scale industrial production. It also exhibits excellent long-term stability, with a service life of over 20 years.

The fatal drawback of CdTe cells, however, lies in the toxicity of cadmium. Although cadmium is not released during normal use, special attention must be paid to environmental protection during recycling and disposal. This has limited the application of CdTe flexible modules in regions with strict environmental requirements.

3. Perovskite

Perovskite solar cells are among the most widely discussed photovoltaic technologies in recent years, and their application prospects in the field of flexible photovoltaics are equally promising. The laboratory efficiency of perovskite cells has rapidly increased from 3.8% in 2009 to 26.1% in 2023, surpassing the theoretical maximum efficiency of polycrystalline silicon cells and demonstrating enormous development potential. Perovskite materials can be prepared via solution-based methods, enabling large-area deposition on flexible substrates with simple manufacturing processes and low costs. Moreover, perovskite cells can achieve varying degrees of transparency by adjusting material composition, providing unique advantages for their application in fields such as Building-Integrated Photovoltaics (BIPV).

Nevertheless, the stability of perovskite cells remains the primary bottleneck restricting their commercial application. How to maintain stable long-term performance in humid, high-temperature, and other harsh environments is an urgent issue for researchers to address.

(2) Flexible Crystalline Silicon Cells: Flexible Breakthroughs in Traditional Technology

Traditional crystalline silicon cells (e.g., PERC, TOPCon) are usually brittle and difficult to bend. However, through special technological innovations, a certain degree of flexibility can be achieved, offering an alternative technical option for flexible photovoltaics.

1. Ultra-Thin Silicon Wafer Technology: From “Brittle Rigidity” to “Flexibility”

The silicon wafers used in traditional crystalline silicon cells are typically around 180μm thick. In contrast, flexible crystalline silicon cells reduce the thickness of silicon wafers to less than 100μm (even as thin as 50μm) through thinning technology. These ultra-thin silicon wafers are not only significantly lighter but also possess a certain degree of flexibility.

Currently, flexible crystalline silicon modules using ultra-thin silicon wafer technology can achieve a bending radius of over 50cm. Although less flexible than thin-film cells, they still hold application value in scenarios with low bending requirements.

2. Glass-Free Packaging: A Key Step Toward Flexibility

Traditional crystalline silicon modules usually use glass as packaging material, which not only increases weight but also limits flexibility. In contrast, flexible crystalline silicon cells use polymers (such as ETFE, TPT, etc.) instead of glass, allowing the modules to bend slightly.

The weight of glass-free packaged flexible crystalline silicon modules can be reduced to 5-8kg/m². Although still heavier than thin-film flexible modules, they have an advantage in conversion efficiency, making them suitable for scenarios requiring both efficiency and a certain degree of flexibility.

(3) Organic/Dye-Sensitized Solar Cells

In addition to the two main technical routes mentioned above, organic and dye-sensitized solar cells also occupy a niche in the field of flexible photovoltaics. Although their conversion efficiency is relatively low, they have unique advantages in specific scenarios.

1. Organic Photovoltaics (OPV)

Organic photovoltaics use organic semiconductor materials and can be prepared via solution-based methods, enabling large-area film formation on flexible substrates.

OPV modules can be as thin as less than 0.1mm and can be made into translucent or even fully transparent products, making them suitable for scenarios such as building curtain walls and windows, where aesthetics and power generation functions need to be combined. Organic materials can be produced on a large scale through processes such as printing and coating, featuring low manufacturing costs and compatibility with flexible substrates.

However, the conversion efficiency of OPV is still relatively low (generally around 10%), and its service life is short, which limits its application in large-scale power generation scenarios.

2. Dye-Sensitized Solar Cells (DSSC)

Dye-sensitized solar cells have a unique working principle that allows them to perform well in low-light environments. Under low-light conditions such as indoor lighting or cloudy weather, DSSCs can still generate electricity effectively, making them suitable for providing continuous power to IoT devices and smart home systems. Additionally, DSSCs can achieve a wide range of colors by selecting different dyes, meeting decorative needs.

Currently, DSSCs are mainly used in indoor low-light power generation scenarios, such as powering low-power devices like smart electricity meters and sensors.

III. Five Core Advantages: Flexible Photovoltaics Reshaping the Solar Application Landscape

The reason why flexible photovoltaic modules can subvert the application model of traditional solar panels lies in their five core advantages. These advantages work in synergy to drive innovation in the way solar energy is utilized.

(1) Ultra-Lightweight and Portable: A Revolutionary Breakthrough in Installation Freedom

Traditional photovoltaic modules require heavy supports and complex reinforcement structures, resulting in cumbersome installation processes and high costs. In contrast, flexible photovoltaic modules, with their ultra-lightweight and flexible properties, have completely changed this situation.

Flexible modules can be directly attached to curved surfaces (e.g., car roofs, tents) or installed via suspension, eliminating the need for professional supports and complex construction procedures. For example, when installing flexible photovoltaic modules on the roof of a recreational vehicle (RV), ordinary users can complete the installation with simple tools. In contrast, traditional modules require professional teams for design and construction, and installation costs can be reduced by more than 60%.

Flexible modules can be rolled up for transportation, significantly saving transportation space and costs. A standard container can hold 5-10 times the area of flexible modules compared to traditional modules, reducing transportation costs by over 70%. Meanwhile, rolled storage also reduces the need for warehouse space, making them particularly suitable for scenarios requiring rapid deployment, such as emergency disaster relief.

Thanks to their lightweight and portability, flexible modules can be easily integrated into various mobile devices (e.g., backpacks, drones, electric vehicles), providing continuous power supply for mobile equipment and expanding the application boundaries of solar energy.

(2) Curved Surface Adaptability: Unlocking Unlimited Application Scenarios

Traditional photovoltaic modules can only be installed on flat surfaces, which greatly limits their application scope. In contrast, flexible photovoltaic modules, with their excellent bendability, can adapt to various complex curved surfaces, unlocking unprecedented application scenarios.

Modern architectural design increasingly pursues personalization and artistry, extensively adopting complex curved surfaces such as arcs and spheres. Flexible photovoltaic modules can be directly attached to these curved surfaces, not only realizing solar power generation but also not affecting the aesthetic effect of the building. For instance, on the exterior walls of iconic buildings like museums and stadiums, flexible photovoltaic modules can be perfectly integrated with the architectural design, becoming an integral part of the building.

The shells of transportation vehicles such as cars, ships, and aircraft are usually curved, making it impossible to install traditional photovoltaic modules. However, flexible modules can be easily attached to these curved surfaces to provide auxiliary power for the vehicles. For example, the solar-powered car launched by the Dutch company Lightyear is equipped with flexible photovoltaic modules on its roof and hood, enabling it to travel approximately 70 kilometers per day using solar energy, significantly extending the range of electric vehicles.

In outdoor activities such as adventure and camping, flexible photovoltaic modules can be integrated into equipment like tents, backpacks, and sleeping bags to provide power for devices such as mobile phones, GPS systems, and cameras. For example, some outdoor brands have launched solar tents with flexible photovoltaic modules installed on the tent roof—these modules charge during the day, and at night, they can power lamps, fans, and other equipment inside the tent.

(3) High Impact Resistance: A Reliable Energy Choice in Harsh Environments

Traditional photovoltaic modules use glass packaging, resulting in poor impact resistance and vulnerability to damage in harsh weather such as hailstorms and typhoons. In contrast, flexible photovoltaic modules, which do not use glass, have significantly improved impact resistance, making them suitable for use in harsh environments.

The flexible substrates and packaging materials used in flexible modules have excellent weather resistance, enabling them to maintain stable performance in harsh environments such as high temperatures, low temperatures, and high humidity. For example, in desert areas where daytime temperatures can exceed 50°C and drop below 0°C at night, flexible modules can still work normally; in marine environments, high salt spray corrosion does not cause significant damage to flexible modules.

Tests have shown that flexible photovoltaic modules can withstand impacts from hailstones with a diameter of 25mm traveling at 23m/s without damage, whereas traditional glass-packaged modules are likely to crack under the same conditions. This feature gives flexible modules a distinct advantage in hail-prone areas, such as northwest China. Additionally, the flexibility of these modules allows them to better adapt to vibrating environments such as earthquakes, reducing the risk of cracking or falling off. This is of great significance for photovoltaic applications in earthquake-prone areas.

(4) Excellent Low-Light Performance: A Power Generation Expert in Urban Environments

Traditional crystalline silicon photovoltaic modules have high efficiency under strong light but experience a significant drop in efficiency under cloudy conditions or scattered light. In contrast, some flexible photovoltaic modules—especially thin-film-based flexible modules—maintain good power generation performance in low-light environments, making them highly suitable for urban settings.

On cloudy or overcast days, when solar radiation intensity is low, the power generation efficiency of traditional modules may drop to below 50%, while thin-film flexible modules such as CIGS can still maintain an efficiency of over 70%. This enables flexible modules to generate more actual electricity in cities with complex lighting conditions.

Dye-sensitized solar cells (DSSCs) and some organic photovoltaic (OPV) modules can also generate electricity under indoor lighting. Although their efficiency is relatively low, it is sufficient to meet the power supply needs of some low-power devices. For example, in indoor environments such as offices and shopping malls, DSSC modules can provide continuous power to smart sensors and wireless communication devices without the need for frequent battery replacement.

Urban buildings are densely packed, and the rooftops or walls of many buildings are shaded by surrounding structures, resulting in poor lighting conditions. The low-light performance of flexible modules allows them to generate electricity effectively in these scenarios, improving the utilization of solar energy in urban buildings.

(5) Customizable Design: The Perfect Integration of Functionality and Aesthetics

Flexible photovoltaic modules break free from the fixed form of traditional modules and can be customized according to different application needs, achieving the perfect integration of functionality and aesthetics.

By adjusting battery materials and packaging processes, flexible modules can be made into different colors (e.g., blue, green, red) and even achieve transparent or translucent effects. This allows flexible modules to perfectly match building exteriors and interior decorations, meeting diverse aesthetic needs. For example, installing transparent flexible photovoltaic modules on the glass curtain walls of commercial buildings not only does not affect lighting but also realizes power generation—achieving a “two-in-one” effect.

Flexible modules can be customized into various shapes and sizes (e.g., circular, triangular, irregular shapes) according to the needs of practical application scenarios. This provides architects with more creative space, allowing solar power generation systems to become part of architectural design rather than additional equipment.

Flexible modules can be integrated with traditional building materials (e.g., tiles, wall panels, windows) to form Building-Integrated Photovoltaic (BIPV) products. For example, the “Han Tile” launched by Hanergy combines flexible photovoltaic modules with traditional tiles, featuring both the decorative effect of traditional tiles and power generation capabilities—realizing the dual functions of power generation + architecture.

1. Diverse Application Scenarios: Flexible Photovoltaics Illuminating All Aspects of Life

With their unique advantages, flexible photovoltaic modules are achieving breakthrough applications in multiple fields. Looking to the future, from architecture to transportation, from outdoor to indoor environments, and from large-scale equipment to wearable products, flexible photovoltaics may illuminate every aspect of our lives.