A D1−A−A′−π−D2 type (D = donor; A = acceptor) unsymmetrical small molecule denoted as BTD3 containing different end group donor moieties has been designed and synthesized for use as a donor in the solution processable bulk heterojunction (BHJ) solar cell. The BTD3 exhibits a low HOMO−LUMO gap of 1.68 eV and deeper HOMO energy level (−5.5 eV). Its LUMO energy level (−3.65 eV) is compatible with the LUMO level of PC 71 BM to facilitate the electron transfer from BTD3 to PC 71 BM in the BHJ solar cell. The solution processed BHJ solar cell with optimized BTD3:PC 71 BM active layer processed with THF solvent exhibited a PCE of 3.15% with J sc = 7.45 mA/cm 2 , V oc = 0.94 V, and FF = 0.45. Moreover, the device with optimized concentration of 3 vol. % 1chloronaphthalene (CN) additive, i.e., CN/THF, showed significant enhancement in PCE up to 4.61% (J sc = 9.48 mA/cm 2 , V oc = 0.90 V, and FF = 0.54). The improvement in the PCE has been attributed to the appropriate nanoscale phase separation morphology, balance charge transport, and enhancement in the light harvesting ability of the active layer.

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Billions of IoT devices and smart objects are already in operation today and even more are expected to be on the network over time. These IoT devices will generate enormous amounts of data that cannot be allowed to transmit on the network without end-to-end encryption or any trust and security mechanism. Currently, we have certificate authorities that certify the identity of a network device by binding its identity with its public key. However, these certificate authorities are centralized in structure and will not be able to individually certify billions of IoT devices entirely. In this paper, we propose that in an SDN-based IoT network, the identities, i.e., public keys and trust indices of IoT devices, can be stored on a blockchain to ensure immutability and tamper-resistance. The paper presents a novel scalable solution for key and trust management of IoT devices in IoT networks, with a successful proof-of-concept that proves the scalability of the proposed solution. The combination of an IoT network along with blockchain technology and softwaredefined networking (SDN) is effectively demonstrated through simulation that is able to store the public keys of IoT devices on the blockchain and route the network traffic efficiently through SDN. The performance of the proposed solution is evaluated in terms of throughput and access time delay. The results illustrate that access delay and throughput were not affected linearly or exponentially and the proposed solution shows no significant degradation in the performance with the increase in the number of nodes and packets.

In the present article bulk heterojunction (BHJ) solution processed organic solar cells have been prepared using mono(carboxy)porphyrin-triazine-(Bodipy) 2 triad (PorCOOH)(BDP) 2 as a donor and ([6,6]-phenyl C 71 butyric acid methyl ester) (PC 71 BM) as an acceptor. This donor/acceptor system aims at the of increasing the light capturing process efficiency of the device. The solution processed BHJ organic solar cell with an optimized weight ratio of 1:1 (PorCOOH)(BDP) 2 :PC 71 BM processed with THF as a solvent showed an overall power conversion efficiency (PCE) of 3.48 % with short circuit current J sc = 8.04 mA/cm 2 , open circuit voltage V oc = 0.94 V and fill factor FF =0.46. The relatively high value of V oc was attributed to the deeper highest occupied molecular orbital energy level of (PorCOOH)(BDP) 2 . When the active layer of the solar cell was processed from a mixture of 4% v/v of pyridine in THF solvent, it achieved a PCE value of 5.29 % with J sc =10.48 mA/cm 2 , V oc =0.90 V and FF=0.56. This was ascribed to the enhancement of both the J sc and the FF values. The higher value of J sc is explained by the increased absorption profile of the blend, the stronger incident photon to current efficiency (IPCE) response and the higher crystallinity of the active layer, induced by the solvent additive while the enhancement of FF may be due to the better charge transport capability and the charge collection efficiency in the later device.

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