Structurally colored semitransparent perovskite solar cells using one-step deposition of self-ordering microgel particles

Semitransparent perovskite solar cells (STPSCs) have excellent potential for widespread application as building integrated photovoltaics. Widespread application of STPSCs could result in decreased CO2 footprints for buildings. Unfortunately, STPSCs tend to have poor aesthetic qualities (being usually red-brown in color) and low stability. Building on our previous work, here we use new poly(N-isopropylacrylamide) microgels (PNP MGs) to provide highly ordered non-close packed arrays within perovskite films that reflect some of the incident light to provide structural color to STPSCs. (MGs are swellable crosslinked polymer colloid particles.) We introduce PNP MGs into two different perovskites and achieve a wide gamut of reflected color and iridescence from the perovskite films. Devices containing the MGs have average visible transparency (AVT) values of greater than 25%. The best PCE for a MG-containing STPSC is 10.60% compared to 9.14% for the MG-free control. The MGs not only introduce structural color to the STPSCs but increase the PCE and stability. Equations are provided that enable the reflected color to be predicted from the formulation used to deposit the films. Our work shows that the self-ordering tendency of PNP MGs gives a viable new method for introducing structural color into STPSCs. Because our one-step method for introducing structural color into STPSCs is general, does not introduce any additional processing steps and is scalable whilst also improving device stability, this study may bring deployment of STPSCs closer

Improving the efficiency and stability of perovskite solar cells using π-conjugated aromatic additives with differing hydrophobicities †

Perovskite solar cells (PSCs) continue to excite the research community due to their excellent power conversion efficiency (PCE) and relative ease of preparation. Additive engineering has played a decisive role in improving PSC performance and stability. In particular, π-conjugated aromatic additives (CAAs) offer key advantages such as high charge transport. However, the roles of hydrophobicity and structure in determining CAA performance as additives are still being established. Here, we investigate the effects of two coumarin additives on the PCE and stability of PSCs based on Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 perovskite. The CAAs are coumarin methacrylate (CMA) and coumarin hydroxyethyl (CHE) and were added to the precursor perovskite solutions prior to film deposition with CMA being more hydrophobic than CHE. These additives increase the best PCE of 19.15% for the control to 21.14% and 21.28% for the best devices containing CHE and CMA, respectively. The stability of the devices with the additives are far superior to that of the control (CAA-free) system. The time lengths required for the PCE to decrease to 80% of the initial value for CMA- and CHE-containing devices are 98 and 38 days, respectively, compared to only 14 days for the control. The moisture and thermal stabilities of the systems containing CMA are markedly improved compared to those containing CHE and the control. Our results show that the extents of binding to Pb2+ and passivation increase as the coumarin's hydrophobicity increases which decreases recombination. Our findings show that adding CAAs with increasing hydrophobic character to the precursor perovskite solution is useful for achieving high-performance and long-term stable PSCs