Contrasting Electron and Hole Transfer Dynamics from CH(NH2)2PbI3 Perovskite Quantum Dots to Charge Transport Layers

Abstract

In this work, the ultrafast transient absorption spectroscopy (TAs) was utilized to first investigate the charge transfer from the emerging FAPbI3 (FA = CH(NH2)2) perovskite quantum dots (PQDs) to charge transport layers. Specifically, we compared the TAs in pure FAPbI3 PQDs, PQDs grown with both electron and hole transfer layers (ETL and HTL), and PQDs with only ETL or HTL. The TA signals induced by photoexcited electrons decay much faster in PQDs samples with the ETL (~20 ps) compared to the pure FAPbI3 PQDs (>1 ns). These results reveal that electrons can effectively transport between coupled PQDs and transfer to the ETL (TiO2) at a time scale of 20 ps, much faster than the bimolecular charge recombination inside the PQDs (>1 ns), and the electron transfer efficiency is estimated to be close to 100%. In contrast, the temporal evolution of the TA signals in the PQDs with and without HTL exhibit negligible change, and no substantive hole transfer to the HTL (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], PTAA) occurs within 1 ns. The much slower hole transfer implies the further potential of increasing the overall photo-carrier conversion efficiency through enhancing the hole diffusion length and fine-tuning the coupling between the HTL and PQDs.

Synergetic interfacial passivation, band alignment, and long-term stability with halide-optimized CsPbBrxI3−x nanocrystals for high-efficiency MAPbI3 solar cells

“…To further explore the carrier dynamics of the photoactive layer with NCs and HTLs, transient absorption spectroscopy (TA) measurement [27][28][29][30] was performed, as shown in Fig. 6b.…”

Advances to High‐Performance Black‐Phase FAPbI3 Perovskite for Efficient and Stable Photovoltaics

“…It is reported that the charge transfer ability in FAPbI 3 QDSCs depended on the interfacial interaction between the PQD/charge transport layer heterojunctions. [43,44] To achieve efficient charge separation and transfer in FAPbI 3 QDSCs, introducing small or polymer molecule with conjugated structure in PQDs could enhance charge carrier extraction and reduce recombination at PQD/charge transport layer interfaces. [45,46] As a result, the PCE of FAPbI 3 PQDs-based devices could achieve 13%.…”

Effective Hole Transfer from CH(NH2)2PbI3 Perovskite Quantum Dots to Conjugated Polymers: A Bridge for Carrier Extraction by the Organic Hole-Transporting Layer

“…These layers facilitate the extraction of charge carriers and minimize the internal recombination. The ultrafast charge transfer (CT) relies on the electronic coupling and interfacial interaction between PQDs and charge-transporting layers . The efficiency of hole transfer from pure PQDs to the HTL may not be satisfactory, in particular for the HTL PTAA, , which has higher hole mobility and is cheaper than Spiro-OMeTAD and considered as the ideal choice for the practical device applications.…”

“…The ultrafast charge transfer (CT) relies on the electronic coupling and interfacial interaction between PQDs and charge-transporting layers . The efficiency of hole transfer from pure PQDs to the HTL may not be satisfactory, in particular for the HTL PTAA, , which has higher hole mobility and is cheaper than Spiro-OMeTAD and considered as the ideal choice for the practical device applications. The ineffective hole extraction due to the large surface energy difference between PQDs and an organic HTL is one of the main reasons limiting the power conversion efficiency (PCE) of perovskite-based devices. , A heterointerface consisting of a conjugated polymer and PQDs is an alternative strategy to provide an additional channel to facilitate the CT .…”