Laboratory scale monolithic perovskite/silicon solar cells (TSCs) (1 cm 2 active area) achieve PCEs up to 23.7%. This work marks a significant advancement for wide bandgap two-step solution-processed perovskite films, enabling their effective use in high-performance and reproducible PSCs and perovskite/silicon TSCs.
In order to facilitate guess at the appropriate layered-composition, the influence of band alignment on solar cell performance is studied in detail. Materials offering easy bandgap tunability are discussed. Electron affinity optimization is shown to lead us to a good band alignment and ultimately avails the way to control band offsets.
The determined optimum bandgap pairings for such sub-cells are well within the range of typical absorber materials. In general, WBG perovskites and GaInP are ideal top cell candidates while crystalline silicon, CIGS, NBG perovskites, and InP are ideal bottom cell candidates for 3T TSCs in voltage-matched strings with VMRs of 1:2 or 2:3.
Moreover, the bandgap and electron affinity for different compositions is calculated by extrapolation of experimental curves. Such technique is followed to obtain the equations (4), (5), (5), (6) for Cd (1-x) Zn x S and CZTS (1-x) Se x. These are further utilized to deduce the equation to calculate bandgap and electron affinity theoretically.
This work introduces an effective and facile strategy to increase the bandgap of two-step solution-processed perovskite films by incorporating bromide in both deposition steps, the inorganic precursor deposition (step 1, PbBr 2) and the organic precursor deposition (step 2, FABr).
Along with electron affinity, energy bandgap, acceptor/donor carrier concentration, activation energy and layer defect density are also explored to obtain tuned energy levels for better band alignment and offsets control.