Proceedings of Online International Conference on Hybrid and Organic Photovoltaics (OnlineHOPV20)
Publication date: 22nd May 2020
Among alternative energy sources, Perovskite Solar Cells (PSCs), raising in efficiency from 3.2% to 22-25.2%
in only few years[1]P3HT has attracted great interest as a polymeric hole-selective material for
perovskite solar cells, due to its scalable solution processability, high efficency[2], high thermal
stability, low cost, relatively high hole mobility (0.1 cm 2 V -1 s -1 ), oxygen impermeability, wide band-
gap ,robust hydrophobicity and superior sealant ability.[3] . P3HT structure was modulated in molecular
weight (MW, 20 to 350 kDa) and regioregularity (RR, 78-100%), to search for correlations between
structure and solar cell efficiency and stability .[3] The P3HT were prepared by different synthetic methods
(oxidative,[4] C-H activation[5] and Grignard Methatesis[6]). Different (MW and RR) P3HT polymers has
been used as hole transport layer (HTM) for Perovskite solar cell devices (PSCs) reaching a
photoconversion efficiency of 17.6% confirming their good potential as HTMs for PSCs. We observed a
remarkable trend relating the thermal stability, the RR and the MW of the P3HT polymers. The outcome is
an enhancement in efficiency, thermal stability of encapsulated perovskite photovoltaic devices resulting
from increasing both MW and RR of P3HT. Moreover, devices fabricated with P3HT as HSL having a MW of
338kDa could retain 80% of their initial efficiency after thermal stress at 85°C after 1000 hours. MW tuning
to higher values seems to reduce the amount of recombination centers, as also confirmed by EIS and dark
JV results. Concerning the light stability, the 338 kDa MW P3HT, characterised by a face-on structural
arrangement yields the most stable device,.. GIWAXS measurement shows that two different
orientations of the crystalline P3HT domains are identified as (100) reflections due to the lamella
layer structure and the (010) reflections due to π-π inter-chain stacking. The preferential
orientation of these axes are varied by MW and RR .The results shows that both the MW and RR are a key
factor for light, thermal stability, strictly correlated to edge-on or face-on polymeric arrangement, mainly
driven by RR.
This work was supported by the Italian Ministry of Economic Development in the framework of the Operating Agreement with ENEA for Research on the Electric System.