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

Abstract

derivatives of polythiophene, derivatives of fullerene, TiO 2 , CdSe, and CuInS 2 , etc., have been used for fabricating solar cells (SCs). [1][2][3][4][5][6][7][8][9][10][11] 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), [12][13][14] 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. The prominent progress have been achieved in the power conversion efficiency (PCE) from <1% in 2011 to over 5% in 2017 through designing polymer, synthesizing NCs, passivating NCs, and optimizing device structure, etc. [15][16][17][18][19][20][21][22][23][24][25][26] Though the present record PCE of 5.64% is still far behind other PV devices, the insistence of aqueous solvent is significant in the long term. [27] In order to improve the performance of the AHSCs, we developed an effective way to enhance the short-circuit current (J sc ) by controlling the thickness of the active layer. [27] Devices with thin active layer generate relative higher fill factor (FF) but less light absorption. Therefore, the active layer is thickened to obtain more carriers for higher efficiency, and the record PCE of 5.64% is achieved. However, thick active layer results in redundant carriers that cannot reach to the electrodes due to their restricted transport length, increasing the probability of carrier recombination. As a consequence, the leading efficiencies are mainly hovering around ≈5.5%. Therefore, it is a key step to promote the extraction of the carriers in order to minimize their recombination and extend their transport length.To address this issue, an effective method is to create extensive interfaces for exciton dissociation and charge transfer between donor and acceptor. Bulk heterojunction (BHJ) is confirmed to be a successful structure to realize this aim and hence promote the carrier extraction. [28] PCE above 11% have been achieved recently based on oil-phase fullerene-free SCs. [29] Besides, hybrid photoconductive cathode assisted polymer SCs also achieved PCE above 10%. [30][31][32] However, the contact Aqueous-solution-processed solar cells (ASCs) are promising candidates of the next-generation large-area, low-cost, and flexible photovoltaic conversion equipment because of their unique environmental friendly property. Aqueoussolution-processed polymer/nanocrystals (NCs) 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. In this work, double-side bulk heterojunction (BHJ), in which one BHJ combines the active material with electron transport material and the other combines the active material...

Highly Efficient Aqueous‐Processed Hybrid Solar Cells: Control Depletion Region and Improve Carrier Extraction

“…[31,32] As shown in Figure 4d, the decay dynamics of ZnO:CdTe film are faster, which means better electron extraction efficiency compared with TiO 2 :CdTe films. [2,5,[7][8][9]13,15,17,[33][34][35][36][37][38][39][40] It is shown that the highest PCE (6.51%) and J sc (19.5 mA cm −2 ) have been obtained in this work. As a result, the probability of carrier recombination process becomes smaller.…”

“…This device presents a J sc of 19.5 mA cm −2 , V oc of 0.620 V, FF of 53.9%, and PCE of 6.51%. In our previous work, [17] it was confirmed that thicker photoactive layer improved the probability of the carrier recombination. As a comparison, the corresponding parameters of Device B are 18.8 mA cm −2 , 0.614 V, 50.8%, and 5.87%, respectively.…”

“…are developed to address these issues. [17] In that work, one BHJ is consisted of CdTe and TiO 2 NCs and the other is CdTe NCs and PPV. [15] Jin et al achieved a record PCE of 5.64% (as reported) based on PPV and CdTe NCs by optimizing device structure.…”

“…[17] In that work, one BHJ is consisted of CdTe and TiO 2 NCs and the other is CdTe NCs and PPV. The highest PCE as high as 6.01% was achieved based on ASCs.…”

“…[9,17,[22][23][24][25] The change of photocurrent density (J ph ) versus the internal voltage (V in ) is measured according to the following formula [9,17,[22][23][24][25] The change of photocurrent density (J ph ) versus the internal voltage (V in ) is measured according to the following formula…”