This paper exploits the idea of cross-layer design for wireless sensor networks to improve the network performance. We present a new energy efficient cooperative routing scheme with space diversity using space-time block codes (STBCs) while improving the link's energy-efficiency. In our solution, the selected multiple nodes act as multiple transmitting and receiving antennas. Full diversity from the orthogonal STBC is utilized to overcome multipath fading and to enhance power efficiency. The network performance measures, such as, network throughput and delay are analyzed via an M/G/1 queueing model. The energy consumption and protocol efficiency are also investigated. The results illustrate that our proposed method outperforms the traditional single relay routing method and the single receiving diversity routing method.