| Organic-inorganic hybrid solar cells,which apply the conjugated polymers as electron donors and inorganic semiconducting nanocrystals(NCs)as electron acceptors have attracted much attention in recent years due to the combined the virtues of organic and inorganic materials,low cost and good process ability.However,the device performance of organic-inorganic hybrid solar cells is relatively low,mainly because the micro-morphology of the active layer is difficult to control.At present,the active layers of organic-inorganic hybrid solar cells are mainly prepared by physically blending of conjugated polymers and inorganic semiconducting NCs.Owing to the poor compatibility between the conjugated polymers and the inorganic NCs,the inorganic semiconducting NCs are easy to aggregate in conjugated polymers and the macroscopic phase separation is prone to occur,which leads to the low exciton dissociation efficiency.Meanwhile,the interface between the conjugated polymers and the inorganic NCs is not intimate,which is not beneficial to the charge transfer.Therefore,formation of intimate hybrid contact between conjugated polymers and inorganic semiconducting nanocrystals and simultaneously obtaining a continuous interpenetrating network on the nanoscale is the key to improve the efficiency of hybrid solar cells.In this paper,two approaches are applied to improve the compatibility between polymers and NCs for the fabrication of the conjugated polymers/inorganic semiconducting nanocrystals hybrid material systems with intimate hybrid interface and continuous interpenetrating network structure.The main research contents are as follows:Firstly,the all-conjugated amphiphilic polythiophene block copolymers:poly(3-hexylthiophene)-block-poly(3-triethylene glycol-thiophene)(P3HT-b-P3TEGT)were synthesized as electron donors and the water-soluble CdTe NCs were synthesized as the electron acceptors.The good compatibility between the hydrophilic P3TEGT blocks and the water-soluble CdTe nanocrystals promotes the uniform dispersion of the CdTe nanocrystals in P3HT-b-P3TEGT.At the same time,the in-situ thiocyanate passivated CdTe nanocrystals were synthetized by introducing ammonium thiocyanate ligands during the synthesis of CdTe NCs.The results showed that in-situ inclusion of thiocyanate could further improve the dispersion of CdTe NCs in P3HT-b-P3TEGT,effectively increasing the hybrid interface area of polymers and inorganic NCs.As a result,the nanoscale continuous interpenetrating network with intimate hybrid interface was formed and the efficiency of exaction dissociation and charge transfer were improved.Meanwhile,in-situ inclusion of thiocyanate ions could effectively regulate the size,crystallinity and photoluminescence of CdTe NCs.In addition,thiocyanate ions could passivate the surface defects of CdTe NCs and inhibit the formation of oxides,improving the stability of nanocrystals.The device results showed that the efficiency of charge extraction and transfer was greatly improved by employing such P3HT-b-P3TEGT/CdTe hybrid films.Secondly,the P3HT/GaN heterojunction with intimate hybrid interface was fabricated by in-situ growth of GaN nanocrystals in P3HT matrix using atomic layer deposition(ALD)technique.The effects of different growth cycles on the micromorphologies,photophysical properties and photocurrent density of P3HT/GaN hybrid films were investigated.The results showed that the performance of devices based on P3HT/GaN thin films were greatly improved compared to devices using the pristine P3HT,indicating that more hybrid interface was formed with the growth of GaN nanocrystals.When GaN nanocrystals were grown for 80 cycles,the photocurrent density of the device was optimized.However,when the growth period of GaN is over 80 cycles,the photocurrent density of the device decreased.The results indicated that over-growth of GaN nanocrystals severely disturbed the crystallinity of polymer P3HT and decreased the ordering stacking of the P3HT molecular chains,which decreased the carrier transport. |
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