The incorporation of graphene related materials (GRMs) have brought fresh air in the field of perovskite (PeSCs) solar cells. GRMs can simultaneously or individually optimize the photovoltaic parameters by taking advantage of their high charge mobility to provide additional percolated pathways for efficient exciton dissociation and charge transport in the photoactive layer, by adopting universal work function (WF) tunable charge transport layers, capable of providing a perfect energy match for either hole or electron extraction, and to fabricate flexible TCEs with tailored optoelectronic properties. In this context, GRMs have been successfully employed by my group in all the major components of a PeSC with a variety of functions [ChemSusChem 2016, 9, 3040; Adv. Energy Mater. 2017, 7, 1602120; Adv. Energy Mater. 2018, 8, 1702287; Energy Environ. Sci. 2018, 11, 1030]. 

In this talk, I will highlight our recent progress in improving the PeSCs lifetime through 2D interfacial engineering, and analysis of the degradation processes under prolonged illumination. The introduction of MoS2 flakes as a hole extraction interlayer in inverted PeSCs, resulted in significant improvement in the device lifetime, which is attributed to the stabilization of the hole transport layer/perovskite interface, inhibiting the bulk degradation process of the perovskite structure itself. In this way, encapsulated PeSCs with MoS2 interlayer retained 80% of their initial PCE (T80) after ~568 hours of continuous illumination at maximum power output in ambient conditions. This is, to date, the highest ever-reported lifetime for PeSCs tested in these conditions (Adv. Energy Mater 2018, 8, 1702287). Furthermore, solution-processed, high-quality electrochemically exfoliated graphene (EG) was employed as an effective dopant for the conventional HTM PTAA, to realize planar inverted PeSCs exhibiting extremely improved stability and PCE. EG doped PTAA as the HTL significantly improved hole extraction, while the device lifetime was also increased compared to the control device with F4-TCNQ doped PTAA. Moreover, EG was applied as a flexible ITO alternative TCE obtained by spray-coating, to realize efficient planar inverted PeSCs. EG based TCEs thickness was accurately optimized to improve the tradeoff between transparency and conductivity, achieving high PCE values of ~11% and 9.8% for rigid and flexible PeSCs, respectively. The PCE of the champion flexible PeSC was sustained at ~90% of their initial value, without increase in sheet resistance upon bending tests of 1000 bending cycles, proving that highly reproducible EG spray-coated TCEs hold enormous promise for both rigid and flexible large‐scale PeSCs, bringing the gap between graphene‐based and ITO electrodes, for next generation flexible PeSCs.

The incorporation of graphene related materials (GRMs) have brought fresh air in the field of perovskite (PeSCs) solar cells. GRMs can simultaneously or individually optimize the photovoltaic parameters by taking advantage of their high charge mobility to provide additional percolated pathways for efficient exciton dissociation and charge transport in the photoactive layer, by adopting universal work function (WF) tunable charge transport layers, capable of providing a perfect energy match for either hole or electron extraction, and to fabricate flexible TCEs with tailored optoelectronic properties. In this context, GRMs have been successfully employed by my group in all the major components of a PeSC with a variety of functions [ChemSusChem 2016, 9, 3040; Adv. Energy Mater. 2017, 7, 1602120; Adv. Energy Mater. 2018, 8, 1702287; Energy Environ. Sci. 2018, 11, 1030]. 

In this talk, I will highlight our recent progress in improving the PeSCs lifetime through 2D interfacial engineering, and analysis of the degradation processes under prolonged illumination. The introduction of MoS2 flakes as a hole extraction interlayer in inverted PeSCs, resulted in significant improvement in the device lifetime, which is attributed to the stabilization of the hole transport layer/perovskite interface, inhibiting the bulk degradation process of the perovskite structure itself. In this way, encapsulated PeSCs with MoS2 interlayer retained 80% of their initial PCE (T80) after ~568 hours of continuous illumination at maximum power output in ambient conditions. This is, to date, the highest ever-reported lifetime for PeSCs tested in these conditions (Adv. Energy Mater 2018, 8, 1702287). Furthermore, solution-processed, high-quality electrochemically exfoliated graphene (EG) was employed as an effective dopant for the conventional HTM PTAA, to realize planar inverted PeSCs exhibiting extremely improved stability and PCE. EG doped PTAA as the HTL significantly improved hole extraction, while the device lifetime was also increased compared to the control device with F4-TCNQ doped PTAA. Moreover, EG was applied as a flexible ITO alternative TCE obtained by spray-coating, to realize efficient planar inverted PeSCs. EG based TCEs thickness was accurately optimized to improve the tradeoff between transparency and conductivity, achieving high PCE values of ~11% and 9.8% for rigid and flexible PeSCs, respectively. The PCE of the champion flexible PeSC was sustained at ~90% of their initial value, without increase in sheet resistance upon bending tests of 1000 bending cycles, proving that highly reproducible EG spray-coated TCEs hold enormous promise for both rigid and flexible large‐scale PeSCs, bringing the gap between graphene‐based and ITO electrodes, for next generation flexible PeSCs.