Conformal monolayer contacts with lossless interfaces for perovskite single junction and monolithic tandem solar cells

The rapid rise of perovskite solar cells (PSCs) is increasingly limited by the available charge-selective contacts. This work introduces two new hole-selective contacts for p–i–n PSCs that outperform all typical p-contacts in versatility, scalability and PSC power-conversion efficiency (PCE). The molecules are based on carbazole bodies with phosphonic acid anchoring groups and can form self-assembled monolayers (SAMs) on various oxides. Besides minimal material consumption and parasitic absorption, the self-assembly process enables conformal coverage of arbitrarily formed oxide surfaces with simple process control. The SAMs are designed to create an energetically aligned interface to the perovskite absorber without non-radiative losses. For three different perovskite compositions, one of which is prepared by co-evaporation, we show dopant-, additive- and interlayer-free PSCs with stabilized PCEs of up to 21.1%. Further, the conformal coverage allows to realize a monolithic CIGSe/perovskite tandem solar cell with as-deposited, rough CIGSe surface and certified efficiency of 23.26% on an active area of 1 cm2. The simplicity and diverse substrate compatibility of the SAMs might help to further progress perovskite photovoltaics towards a low-cost, widely adopted solar technology. / BMBF, 03SF0540, Nachwuchsgruppe MeSa-Zuma: Entwicklung von spektral optimierten, hocheffizienten und langzeitstabilen Perowskit/Silizium Tandem Solarzellen / BMWi, 0324076B, Verbundvorhaben: EFFCIS - Effizienzoptimierung von CIS-basierten Dünnschichtsolarzellen und -modulen; Teilvorhaben: Insitu-Wachstumsanalytik und optoelektronische Charakterisierung von Cu(In,Ga)Se2 und Cu(In,Ga)(S,Se)2 Dünnschichten für hocheffiziente Dünnschichtsolarzellen / BMWi, 0324095D, Verbundvorhaben: speedCIGS - Rechnerunterstützte Optimierung des CIGS-Depositionsprozesses in der industriellen Umsetzung; Teilvorhaben: Alkalibehandlung der CIGS Absorberoberfläche und monolithisch integrierte Tandem Zelle (p-TCM) / EC/H2020/763977/EU/Perovskite Thin-film Photovoltaics (PERTPV)/PERTPV