Chemical vapor deposition grown formamidinium perovskite solar modules with high steady state power and thermal stability

Abstract

Metal organic halide perovskites are promising materials for solar cells with a maximum certified efficiency of 22.1%. However, there are only a handful of reports on larger area modules, where efficiencies drop with increasing use of the active area. Chemical vapor deposition (CVD) is a technology used in many industrial applications demonstrating potential for scale up. We used a CVD process to fabricate MAPbI₃ and FAPbI₃ based solar cells with power conversion efficiencies (PCEs) up to 15.6% (MAI, 0.09 cm²) and 5 × 5 cm modules with 9.5% (FAI, 5-cell modules, total active area 8.8 cm²) and 9.0% (FAI, 6-cell modules, total active area 12 cm²). To further investigate scaling issues, we fabricated modules using an established MAPbI₃ solution process, and demonstrated maximum PCEs of 18.3% (MAI, 0.1 cm²), 14.6% (MAI, 1 cm² single cells), and 8.5% at 5 × 5 cm (MAI, 6-cell module, total active area 15.4 cm²). The solution processed cells performed better than CVD cells when comparing PCEs determined from J–V measurements, but the steady state power of solution processed solar cells decreased quickly with increasing area. This decrease in power was correlated with rapid heating of the solar cells under 1 sun illumination, with a pronounced drop in performance at the phase transition temperature of MAPbI₃. In contrast, FAPbI₃ CVD grown solar modules maintained much of their PCEs transitioning from J–V measurements to the steady state operating conditions (1 sun), suggesting that the FAI based CVD process may outperform MAI based solution processed modules when scaled up to practical sizes.