Influence of an Inorganic Interlayer on Exciton Separation in Hybrid Solar Cells

Abstract

It has been shown that in hybrid polymer–inorganic photovoltaic devices not all the photogenerated excitons dissociate at the interface immediately, but can instead exist temporarily as bound charge pairs (BCPs). Many of these BCPs do not contribute to the photocurrent, as their long lifetime as a bound species promotes various charge carrier recombination channels. Fast and efficient dissociation of BCPs is therefore considered a key challenge in improving the performance of polymer–inorganic cells. Here we investigate the influence of an inorganic energy cascading Nb2O5 interlayer on the charge carrier recombination channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)–TiO2 and PbSe colloidal quantum dot–TiO2 photovoltaic devices. We demonstrate that the additional Nb2O5 film leads to a suppression of BCP formation at the heterojunction of the P3HT cells and also a reduction in the nongeminate recombination mechanisms in both types of cells. Furthermore, we provide evidence that the reduction in nongeminate recombination in the P3HT–TiO2 devices is due in part to the passivation of deep midgap trap states in the TiO2, which prevents trap-assisted Shockley–Read–Hall recombination. Consequently a significant increase in both the open-circuit voltage and the short-circuit current was achieved, in particular for P3HT-based solar cells, where the power conversion efficiency increased by 39%.

Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices

“…S2H). Furthermore, tetracene acts as an efficient electron-blocking layer because of the substantial difference between its lowest unoccupied molecular orbital and the conduction band of perovskite, a characteristic that could therefore diminish carrier recombination ( 37 ).…”

Quantum‐Tunneling Metal‐Insulator‐Metal Diodes Made by Rapid Atmospheric Pressure Chemical Vapor Deposition

“…The need for high temperatures, specific metal films for oxidation, and complex compound precursors in these techniques, as well as challenges in reproducibility, highlight the need for new methods to reliably deposit enabling films for cost‐effective quantum devices. Recently, atmospheric pressure spatial atomic layer deposition (AP‐SALD) systems have been utilized to grow uniform films for different applications including solar cells, transistors, and light emitting diodes . AP‐SALD is a fast and scalable thin film deposition technique that can operate at atmospheric pressure in the open air (i.e., no deposition chamber).…”

Spatial Atomic Layer Deposition

“…The same group has dedicated efforts to deposit transparent conductive oxides (TCO) layers and more complex oxides for application in photovoltaic devices [51,56,84,85]. Prof. Driscoll's group was the first one to apply the SALD technique for the deposition of active layers for new-generation solar cells [52,[71][72][73][74]. For example, Muñoz-Rojas et al showed that a 15-nm thick amorphous TiO 2 layer can act as an efficient hole blocking layer in bulk heterojunction solar cells [72].…”

“…Intrinsic metal oxides HfO 2 [11] Al 2 O 3 [14-16, 19-21, 26, 31, 35-50] ZnO [18,36,39,45,46,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] SnO x [68,69] TiO 2 [14,18,[70][71][72] Cu 2 O [46,73,74] Nb 2 O 5 [71] NiO x [91] ZrO 2 [92,93] MoO x [94] Doped SALD has also been used for LEDs, in some cases to deposit active ZnO layers for polymer and hybrid perovskite-based diodes [54,76], and in another case using Al 2 O 3 as permeation barrier for flexible organic LEDs [49]. Other authors have also demonstrated the suitability of SALD for depositing barrier and encapsulation layers both on plastic and paper substrates [14,31,40,48].…”