Integrated Calendar

Perovskite solar cells have experienced a very rapid rise in efficiency over the last few years with 20% solar conversion efficiency having been achieved in thin films. Most of the work has been on materials and devices fabricated using solution growth techniques, and with organic heterojunction layers. Some major potential problems that the perovskite cells face are their poor stability under prolonged illumination, and thermal instability. In this talk, I will discuss perovskite cells produced using vapor deposition techniques, and also address the light-induced instability of both p-i-n and n-i-p cells. It will be shown that p-i-n cells are extremely unstable under full spectrum illumination when deposited on PEDOT, but are more stable when deposited on inorganic p type heterojunctions. The n-i-p cells are much more stable than p-i-n cells but still degrade significantly under full spectrum light. I will also discuss the physics of transport in perovskite cells produced using methyl-ammonium iodide, and formamidinium iodide. It will be shown that the transport in perovskite cells is field-assisted and not diffusion-assisted. The results on stability indicate that for tandem cells, the perovskite cells should use inorganic heterojunction layers, and preferably be of the type with the n-layer facing down.