Pitfalls and prospects of optical spectroscopy to characterize perovskite-transport layer interfaces

Abstract

Perovskite photovoltaics has witnessed an unprecedented increase in power conversion efficiency over the last decade. The choice of transport layers, through which photo-generated electrons and holes are transported to electrodes, is a crucial factor for further improving both the device performance and stability. In this perspective, we critically examine the application of optical spectroscopy to characterize the quality of the transport layer-perovskite interface. We highlight the power of complementary studies that use both continuous wave and time-resolved photoluminescence to understand non-radiative losses and additional transient spectroscopies for characterizing the potential for loss-less carrier extraction at the solar cell interfaces. Based on this discussion, we make recommendations on how to extrapolate results from optical measurements to assess the quality of a transport layer and its impact on solar cell efficiency.

Enamine‐Based Cross‐Linkable Hole‐Transporting Materials for Perovskite Solar Cells

“…As the extraction abilities of the material should be independent of the concentration, such a behavior can be attributed to insufficient coverage of the ITO substrate and increased direct contact between the perovskite and ITO. [ 35 ] As a result of increased interface recombination, the reduction in V oc is observed. Overall, an optimized PCE of 18.1% for the cross‐linked films prepared from the 1.5 mg mL −1 solutions was achieved.…”

Consistent Interpretation of Electrical and Optical Transients in Halide Perovskite Layers and Solar Cells

“…Nevertheless, TPL on perovskites samples is mainly measured on pure films, because the interpretation of data obtained on multilayer samples is challenging due to the superposition of various effects that modulate the charge-carrier concentration in the perovskite layer and thereby the measured PL. [47][48][49] TPL measured on thin perovskite films on glass is a frequently used method to derive the recombination rate constants of trap-assisted SRH, radiative, and Auger recombination in the bulk material. [50][51][52] Given that TPL is generally performed as a large-signal (LS) method (i.e., without bias light), the decay is usually too complex to of the transient PL measured on perovskite films (filled symbols) or on perovskite/transport layer stacks (blank symbols) with the stated decay time τ TPV SS resulting from transient photovoltage measurements on the respective solar cell device.…”

Impedance spectroscopy for perovskite solar cells: characterisation, analysis, and diagnosis

“…While in principle, all solar cell operating points correspond to a steady state condition (after a characteristic waiting time), quasi-equilibrium is a particular feature of the VOC. At VOC, all photogenerated charge ultimately recombines radiatively, and all electronic processes, drift, diffusion, charge transfer, are reversible and therefore VOC is a clearly defined operating point for extracting dynamics of electronic processes 63 .…”