Why Thick Perovskite Solar Cells Lose Efficiency — And a Simple Way to Fix It

Abstract

Thick perovskite solar absorbers promise enhanced light capture and module durability but often suffer efficiency losses due to lattice strain relaxation. Recent studies have demonstrated that preserving compressive strain in films over ~2 µm via controlled crystallization methods can elevate power conversion efficiencies (PCEs) from ~17% up to ~23.5%, demonstrating performance comparable to thin films while enhancing long-term stability.1-5

Introduction

Metal halide perovskite solar cells (PSCs) are widely recognized for their high absorption coefficients, solution processability, and potential for low-cost, flexible photovoltaic modules.1 However, as perovskite active layer thickness increases beyond ~1 µm, device performance often deteriorates - manifested in lowered short-circuit current density, reduced fill factors, and increased series resistance.2 This raises a question: what underlying mechanism causes these declines when diffusion length and carrier lifetime remain sufficiently long?

Identifying Lattice Strain as a Key Limitation

Recent investigations have shown that residual lattice strain - compressive or tensile - within perovskite films contributes significantly to performance loss in thick devices. Zhao et al. showed that films subjected to thermal expansion mismatches develop strain during annealing that accelerates ion migration and degradation, especially under continuous illumination.2 Similarly, Shi et al. found that thick films (micron scale) suffer lattice relaxation if strain is not kinetically preserved, resulting in diminished charge transport and reduced PCE.1

Techniques to Preserve Strain and Improve Performance

One effective strategy is in situ passivation during crystallization, as demonstrated by Huang et al., achieving highly oriented crystallites and boosted efficiencies (26.7% certified) using additives to control boundary defects and interfaces.3 Another method involves defect passivation to mitigate recombination pathways arising from strain-related defects. Tan, Huang, and Yang showed that careful passivation reduces trap densities and improves carrier lifetimes in stressed perovskite films.4 Also of note, Guo et al. demonstrated that a structured 2D/3D perovskite hybrid capped film with ultralong carrier lifetimes (>20 µs) and diffusion lengths exceeding ~6.5 µm yields high PCEs (~24.7%) with enhanced stability over hours of continuous operation.5

Performance Gains and Stability Outcomes

• Thick-film PSCs where strain is controlled show PCE improvements from ~17% (baseline thick films) to ~23‑24% while retaining much of their initial efficiency under stress.3
• Devices with reduced residual strain demonstrate slower degradation under heat, moisture, or illumination cycling. Zhao et al. reported that compressively strained films show significantly improved operational stability vs. unstrained controls.2
  
  

Implications for Scalable Manufacturing and Applications

Stable thick perovskite films are critical for module-level fabrication (large area coverage), tandem cell architectures (where perovskite is one of multiple absorbing layers), and flexible form-factors. Methods such as in situ passivation, strain-compensated HTL/substrate selection, and defect passivation are proving feasible with current solution-processing techniques (spin-coating, blade coating).3-5

 

FAQs

Why do thicker perovskite solar cells lose efficiency?

Thicker perovskite solar cells often display incomplete charge extraction, increased interfacial recombination, and non-uniform crystal growth. These issues limit both the efficiency and stability of the device, especially at scale.

Can thick perovskite layers be used in tandem solar cells?

Yes, thick perovskite absorbers are particularly relevant for tandem solar cells, where maximizing light absorption is important. To achieve efficient and stable operation, researchers must focus on interface engineering and optimized transport layers.

What role do buried interfaces play in thick perovskite devices?

Buried interfaces, such as the junction between the perovskite and the hole transport layer, matter — a lot. Defects or misaligned energy levels at these interfaces can reduce the efficiency of charge extraction and increase recombination losses in thick films.

How can we improve the performance of thick perovskite solar cells?

Solutions include using high-performance perovskite modules, applying surface sulfidation, optimizing electron transport and hole transport materials, and stabilizing perovskite-substrate interfaces. These techniques can reduce recombination and deliver high-efficiency inverted perovskite architectures.

Are thick perovskite solar cells scalable for commercial use?

With advances in interface engineering, transport materials, and crystallization control, thick perovskite solar cells and modules show strong potential for scalable, commercial applications, particularly in flexible perovskite and all-perovskite tandem solar formats.

 

References

1. Shi, P., Xu, J., Yavuz, I., et al. (2024). Strain regulates the photovoltaic performance of thick‑film perovskites. Nature Communications, 15, 2579. DOI: 10.1038/s41467‑024‑47019‑8
   
   

2. Zhao, J., Deng, Y., et al. (2021). Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells. Science Advances, 7(48), eabk a o5616. DOI: 10.1126/sciadv.aao5616
   
   

3. Huang, Y., Yan, K., Wang, X., et al. (2024). High‑Efficiency Inverted Perovskite Solar Cells via In Situ Passivation Directed Crystallization. Advanced Materials, 36(41), 2408101. DOI: 10.1002/adma.202408101
   
   

4. Tan, S., Huang, T., Yang, Y. (2021). Defect passivation of perovskites in high efficiency solar cells. J. Phys. Energy, 3, 042003. DOI: 10.1088/2515‑7655/ac2e13

5. Guo, J., Wang, B., Lu, D., et al. (2023). Ultralong Carrier Lifetime Exceeding 20 µs in Lead Halide Perovskite Film Enable Efficient Solar Cells. Advanced Materials, 35(28), 2212126. DOI: 10.1002/adma.202212126