Annealing treatment improves the morphology and performance of photovoltaic devices prepared from thieno[3,4-c]pyrrole-4,6-dione-based donor/acceptor conjugated polymers and CdSe nanostructures

Abstract

We have prepared photovoltaic devices based on blend films of CdSe tetrapods and the donor/acceptor conjugated polymer PDTTTPD, which comprises 2,5-di(thiophen-2-yl)thieno [3,2-b]thiophene and thieno [3,4-c]pyrrole-4,6-dione units. The AM1.5 power conversion efficiency (PCE) of a photovoltaic device containing a PDTTTPD/CdSe tetrapod blend (1 : 9, w/w) that had experienced thermal annealing (130 C, 20 min) was three times greater than that of the corresponding device incorporating the as-prepared PDTTTPD/CdSe tetrapod blend (2.9% vs. 1.0%). Synchrotron X-ray reflectivity revealed that annealing (i.e., removal of pyridine ligands from the surfaces of the CdSe tetrapods) caused the thickness of the PDTTTPD/CdSe tetrapod blend film to decrease (and its average density to increase) relative to that of the as-prepared blend film. Transmission electron microscopy and atomic force microscopy revealed that thermal annealing enhanced the degree of aggregation of the CdSe tetrapods and induced denser morphologies, leading to substantially increased charge transport, which enhanced the PCE of the device.

UV‐Ozone Treatment on Cs2CO3 Interfacial Layer for the Improvement of Inverted Polymer Solar Cells

“…After annealing treatment on the blended film by 120 ∘ C with 10 min, the main absorption peak shifts to the 510 nm, and a shoulder absorption peak at 603 nm was observed. The variation of blended P3HT:PCBM absorption spectra should be attributed to the increased order phase of P3HT induced by annealing treatment, which was demonstrated by our pervious works and other groups [25][26][27][28].…”

Aqueous‐Processed Polymer/Nanocrystal Hybrid Solar Cells with Double‐Side Bulk Heterojunction

“…Since the pioneering work reported by Qiao and co‐workers in 2005, varieties of water‐soluble materials such as poly{ N ‐7′‐[(1′,13′‐bis ( N ′, N ′‐diethylamino) tridecanyl)]‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐enzothiadiazole)}, octadecyltrichlorosilane, derivatives of polythiophene, derivatives of fullerene, TiO 2 , CdSe, and CuInS 2 , etc., have been used for fabricating solar cells (SCs) . Aqueous‐solution‐processed polymer/nanocrystal (NC) hybrid solar cells (AHSCs) can effectively integrate the advantages of the polymer (e.g., flexibility and lightweight) and the inorganic NCs (e.g., high mobility and broad absorption), and therefore be considered as an ideal system to further improve the performance of ASCs. For example, AHSCs fabricated by our group have reached an advanced echelon in just a few years.…”

Conjugated Polymer/Nanocrystal Nanocomposites for Renewable Energy Applications in Photovoltaics and Photocatalysis

“…Another electron‐withdrawing moiety, the thieno[3,4‐ c ]pyrrole‐4,6‐dione (TPD) unit, having a symmetrical, rigidly fused, and coplanar structure, is also beneficial for solar cells when it is incorporated in conjugated polymers . The conjugated polymer PDTTTPD, comprising 2,5‐di(thiophen‐2‐yl)thieno[3,2‐ b ]thiophene and TPD moieties, has been incorporated into CdSe tetrapods to investigate the effects of thermal annealing on morphology and device performance …”